Evolution and vulnerability of blue carbon stocks in a continental shelf mud depocenter: Fladen Ground, North Sea

Muddy sediments across continental shelves serve as a reserve for blue carbon and act as a natural carbon sink, supporting the buffering ability of shelf seas against the global rise in carbon dioxide and associated climate warming. However, these areas are also exposed to anthropogenic activities, mainly fishing and bottom trawling, increasing the probability of additional carbon loss by remineralisation. For the successful management of shelf sea carbon stocks, it is thus important to understand the amount of carbon stored, the reactivity of the organic carbon (labile or refractory), and the transfer efficiency of the organic carbon. The transfer efficiency reflects the balance between the sediment accumulation rate and the degradation rate before the material ultimately gets buried. In areas of fast sediment accumulation, carbon will be sequestered quickly, protecting it from natural and anthropogenic disturbances. In areas with very slow sedimentation rates, the carbon will be exposed to disturbances for a longer period. Thus, different areas of the continental shelf with different depositional settings require specific marine management strategies. This study aims to understand the quantity, quality, and transfer efficiency of carbon within the muddy depocenter of the Fladen Ground, North Sea, which provides a case study for investigating the vulnerability of carbon in a relict mud deposit with very low active sedimentation. We present new age-depth models, dry bulk density, and total organic carbon (TOC) measurements from multiple sediment cores and use them to calculate organic carbon accumulation rates for the Fladen Ground.  This area has been exposed to historic and ongoing trawling, offering an opportunity to understand the fate of carbon in relict mud deposits under anthropogenic disturbances.